1. Field of the Invention
The present invention relates to an electromagnetic relay for opening and closing an electrical circuit.
2. Description of Related Art
In a conventional electromagnetic relay, fixed contact retainers having fixed contacts are positioned and a single movable element having movable contacts is moved. Thus, an electrical circuit is closed by bringing the movable contacts and the fixed contacts into contact with each other. The electrical circuit is opened by separating the movable contacts and the fixed contacts from each other. More specifically, the conventional electromagnetic relay has a movable member attracted by an electromagnetic force of a coil, a contact pressure spring for biasing the movable element in a direction for bringing the fixed contacts and the movable contacts into contact with each other, a return spring for biasing the movable element via the movable member in a direction for separating the fixed contacts and the movable contacts from each other and the like.
If the coil is energized, the movable member is driven in a direction for separating from the movable element by the electromagnetic force. The movable element is biased by the contact pressure spring to move so that the fixed contacts contact the movable contacts. Then, the movable member separates from the movable element. For example, details of such the construction are described in Patent document 1 (Gazette of Japanese Patent No. 3321963), Patent document 2 (JP-A-2007-214034) or Patent document 3 (JP-A-2008-226547).
In the conventional electromagnetic relay, an electromagnetic repulsive force arises between contact portions of the movable contacts and the fixed contacts because currents flow in opposite directions in portions where the movable contacts face the fixed contacts. The electromagnetic repulsive force acts to separate the movable contacts and the fixed contacts from each other. Therefore, an elastic force of the contact pressure spring is set to prevent the separation between the movable contacts and the fixed contacts due to the electromagnetic repulsive force.
However, the electromagnetic repulsive force increases as the flowing current increases. Therefore, the elastic force of the contact pressure spring has to be increased in accordance with the increase in the current value. As a result, a body size of the contact pressure spring enlarges, so a body size of the electromagnetic relay enlarges.